The present invention relates to a bush through which to direct a stream of molten metal into a mold, by pouring or injection.
In particular, the bush disclosed is advantageously suitable for use in directing a flow of castable alloy, for example aluminium alloy in the liquid state, into a permanent mold fashioned typically from steel.
Conventional bushes employed for the purpose in question appear essentially as a tubular element, fashioned generally in nickel-chromium cast iron or special steel. One end of such an element connects with the interior of a mold, and the remaining end with an item of equipment from which the stream of molten metal or metal alloy flows into the mold, either freely or pressurized to a greater or lesser degree, according to the casting technique adopted. A bush of this type is usually encircled at least in part by a heating element, typically comprising an electrical resistance, of which the function is to generate thermal energy in such a way that the molten metal can be kept heated and maintained in a fluid state when effectively occupying the bush, i.e. throughout the step in which it is poured or injected into the mold.
In the case of the conventional type of bush thus outlined, the need to supply abundant quantities of heat stems from the fact that the heat held in the molten metal passing through the bush is dissipated in an unwarranted and excessive manner, causing the metal itself to cool to a certain extent. Moreover, it is inevitable that heat will be transmitted to the bush substantially in continuous fashion, even where the resistance is activated intermittently, as the active generating periods ultimately become longer in duration and progressively more frequent. Thus, despite the provision of the heating element to the end of reducing the frequency with which the metal solidifies, causing a blockage of the bush, it happens in molding equipment using conventional bushes that the heat applied to the molten metal tends to be generated at temperatures higher than effectively necessary, resulting in wasted energy and high costs. In addition, the bushes themselves are somewhat costly, prone to wear in a relatively short space of time, and need replacing at notably frequent intervals, signifying repeated and costly stoppages in operation of the molding equipment. A further drawback, by no means unimportant, stems from the use of special metals and their limited workability post-solidification; in effect, the conventional type of bush must be secured to the relative molding equipment using complex clamping mechanisms which are laborious to fit and remove. Accordingly, the object of the present invention is to overcome the aforementioned drawbacks through the adoption of a pouring or injection bush capable of affording notable energy savings and ensuring significantly increased output from the molding equipment, of which the durability is distinctly greater than that of conventional bushes and the design such as to allow fitment to and removal from a mold in an extremely swift and simple manner.